Can someone identify this NTSC video (CRT) monitor problem? Is itsimple?

[[email protected]]

Hello all.. I have a monitor that allows viewing of the retrace and
overscan periods, so I somewhat fond of it. However, it consistently
displays this symptom:

http://www.bobdbob.com/~deneb/ftp/monitor.jpg

The scan lines are disordered near the top of the image. The display
is usually static, but with certain images, some of the lines jump
around a little. The rest of the image is fine and all the controls
work as expected.

Is there a common cause for this? If so, is it easy to fix, or should
I junk it and focus on remembering the good times?

 

[Jeroni Paul]

Hello all.. I have a monitor that allows viewing of the retrace and

overscan periods, so I somewhat fond of it. However, it consistently
displays this symptom:

http://www.bobdbob.com/~deneb/ftp/monitor.jpg

The scan lines are disordered near the top of the image. The display
is usually static, but with certain images, some of the lines jump
around a little. The rest of the image is fine and all the controls
work as expected.

Is there a common cause for this? If so, is it easy to fix, or should
I junk it and focus on remembering the good times?

This is likely a bad electrolytic in the field output circuit. Not a
difficult repair.

 

[[email protected]]

By the way:

The model number is Panasonic BT-S1300N. If anyone has any service
info and could give some hints I'd be very grateful. JP: I can see
your point, I might be able to handle that job. I have bad luck with
TV-type hardware for some reason. I've only ever succeeded in
repairing one once.

 

[Jerry G.]

Very common, there are bad capacitors in the vertical deflection
amplifier. There may be a number of these that have to be changed.
They can be easily verified with an ESR meter. To service this, it is
best to have experience in TV service.



Jerry G..

 

[Franc Zabkar]

The model number is Panasonic BT-S1300N. If anyone has any service
info and could give some hints I'd be very grateful.

I'm not familiar with your monitor, but in general you would locate
the 4-wire cable that connects to the deflection yoke around the
picture tube. The two thinnest wires would connect to a vertical
amplifier IC on the PCB. Since yours is a Panasonic monitor, I would
expect that this IC would be made by Matsushita and would have a part
number beginning with AN. These ICs are often in a SIP package and are
attached to a heatsink. Some designs use a pair of discrete
transistors, also mounted on heatsinks. I'd replace all the
electrolytic capacitors in the vicinity of this IC, and I'd also
reflow its solder joints.

- Franc Zabkar

 

[[email protected]]

Hello all.. I have a monitor that allows viewing of the retrace and

overscan periods, so I somewhat fond of it. However, it consistently
displays this symptom:

I've been going by the canonical repair faq.. and reading through it
for the umpteenth time I discovered a mention of "vertical foldover."
I hadn't seen that before. Is this what's going on in that photo?

Also thank you F.Z., I probably can't screw it up with advice that
clear.

 

[Franc Zabkar]

I've been going by the canonical repair faq.. and reading through it
for the umpteenth time I discovered a mention of "vertical foldover."
I hadn't seen that before. Is this what's going on in that photo?

That's one common symptom of bad caps, another is vertical
non-linearity. You may also see retrace lines and/or digital teletext
data (lines of dots) during the vertical retrace interval.

If you can identify the vertical output IC, then you may find an
application circuit in its datasheet.

You can search for datasheets here:
http://www.datasheetarchive.com/

- Franc Zabkar

 

[[email protected]]

You were right, in case you had any doubt (which you probably did
not). It's an AN5512, and the cap between pins 4 and 8 of that chip
had 90 ohms of series resistance and about 5% of it's labeled
capacitance. I'm off to the local shop to get some electrolytics.

 

[[email protected]]

Monitor's fixed. Thanks to everyone!

 

[larry moe 'n curly]

You were right, in case you had any doubt (which you probably did
not). It's an AN5512, and the cap between pins 4 and 8 of that chip
had 90 ohms of series resistance and about 5% of it's labeled
capacitance. I'm off to the local shop to get some electrolytics.

BTW the repair manual for the monitor is $4.25, plus $9 shipping from
this company:

www.mcmelectronics.com/product/P-BTS1300N-SM

I'm not sure, but I think Panasonic wants $3.01 for it, but with
shipping it could be more.

Two days ago, my Sanyo TV had a similar problem. Most of the vertical
capacitors (all Jamicon brand) measured high ESR but normal
capacitance.

 

[Franc Zabkar]

It's an AN5512, and the cap between pins 4 and 8 of that chip
had 90 ohms of series resistance and about 5% of it's labeled
capacitance.

The sci.electronics.repair FAQ states that ...

"[Vertical foldover] is probably caused by a fault in the flyback
portion of the vertical deflection circuit - a charge pump that
generates a high voltage spike to return the beam to the top of the
screen."

http://www.repairfaq.org/samnew/tvfaq/tvvfold.htm

The cap between pins 4 and 8 of the AN5512 IC is indeed a "flyback"
charge pump cap.

See page 3 of the datasheet:
http://www.datasheetarchive.com/pdf-datasheets/Datasheets-10/DSA-187661.pdf

- Franc Zabkar